smith



Jan. 28, was.

G. W. SMITH 2,028,812

CONTROL SYSTEM FOR BOILER FURNACES Filed May 25, 1954 5 Sheets-Sheet l E Ii 5 L47 57 40 J- 5 14 AH 55 jg'gfi.

INVENTOR 28, fi fi. G. W $M|TH CONTROL SYSTEM FOR BOILER FURNACES Filed May 25, 1934 5 Sheets-Sheet 2 VCLDFVE TORI 6/ mg m m Jan; 28, 1936. Q W SMITH 2,028,812

CONTROL SYSTEM FOR BOILER FURNACES Filed May 25, 1954 S Sheets-Sheet 3 INVENTOR Patented Jan. 28, 1936 UNETED S'iA'lsEd PATENT OFFICE George W. Smith, Pittsburgh, Pa., assignor to John M. Hopwood, Dormont, Pa.

Application May 25, 1934, Serial No. 727,473

16 Claims.

This invention relates to boiler furnaces having control apparatus for automatically adjusting the supply of fuel and air and the draft by and in accordance with changes in load, and. more particularly to apparatus for regulating the draft by and in accordance with changes in the load.

An object of this invention is the provision of a regulating system of the character above referred to, whereby separate but related control impulses may be transmitted to fuel supply and draft regulating apparatus for the purpose of adjusting the fuel supply and draft by and in accordance with changes in the load demand.

Another object of the invention is the provision of apparatus in which the draft losses across the boiler may be reproduced in miniature and varied by and in accordance with the load demand, and by means of which the draft at the furnace outlet may be adjusted by and in accord- QQ ance with changes in draft losses in the suction line.

Another object of the invention is the provision of a conduit or pipe line which is connected at one end to a source of suction and open to the atmosphere at the other end, and provided with a variable orifice and a fixed orifice between the suction source and the variable orifice, and of apparatus responsive to changes in pressure con-- ditions between the orifices for so adjusting the suction source that the pressure between said orifices is maintained substantially constant for all positions of the variable orifice.

A further object of the invention is the provision of means whereby the value of pressure between spaced orifices in a pipe line through which either a gaseous or fluid medium flows may be adjusted to and maintained substantially constant at any desired fraction of the value of the pressure at the source or cause of such fiow.

Other objects of the invention will, in part, be apparent and will, in part, be obvious, from the following description taken in conjunction with the accompanying drawings, in which:

Figure l. is a more or less diagrammatic view of a boiler furnace provided with a control system embodying one form of the invention;

Fig. 2 is a view in section of a suction adjusting valve or orifice embodied in the apparatus of 3 is a view of a regulator for controlling the rate or fuel supply to the furnace;

Fig. 4- is a view in section of a fixed, but adjustable, orifice employed in a suction line of the system of Fig. l, in conjunction with the valve or orifice of Fig. 2;

Fig. 5 is a view in section of a master regulator embodied in the system of Fig. 1;

Fig. 6 is a more or less diagrammatic view, partially in section, of a proportioning relay embodied in the system of Fig. 1;

Fig. '7 is a more or less diagrammatic view of a furnace showing the control apparatus illustrated in Fig. 1 in connection with the control and regulation of the draft, as applied to the regulation of the pressure of the air supply to facilitate and make possible a more accurate control of the supply of combustion air to the furnace; and

Fig. 8 is a more or less diagrammatic view of a boiler furnace provided with a plurality of sources of supply of different fuels, and a control system, such as shown in Fig. 1, for regulating the draft, modified to regulate the draft by and in accordance with the demand for steam and the total amount of fuel delivered to the furnace by such sources of supply.

Throughout the drawings and specification, like reference characters indicate like parts.

In Fig. l of the drawings a boiler furnace l is shown which is provided with apparatus 2 for supplying comminuted or pulverized fuel to the furnace. Combustion air is delivered to the furnace by a pipe or duct 3 to which a forced draft fan (not shown) is connected for supplying the air required. At the outlet of the furnace, a 'conduit 4 conveys the products of combustion to a stack (not shown). Conduit 3, it will be understood, is connected to an induced draft fan (not shown) and is provided with an outlet damper 5 for adjusting the draft.

The outlet damper 5 is connected to a regulator 6 which is controlled by a master regulator M. R. and a proportioning relay P. R. to operate by and in accordance with changes in the load on the boiler, or in the demand for steam, so that the outlet damper will be adjusted to vary or regulate the draft at the outlet of the boiler by and in accordance with the load or demand for steam. Regulator 6 includes an actuating device or motor 1 which operates the damper, and a suction responsive apparatus 8 that controls the motor 1. Apparatus 8 is connected to a suction line 9, one end of which is open to the atmosphere at H] and the other end of which is connected to the outlet of the furnace. In the suction line, a fixed but adjustable orifice II, and a variable orifice l2 are provided. The fixed, but adjustable orifice l2, as shown, is disposed between the outlet of the furnace and the variable orifice. The suction responsive apparatus of regulator 6 is connected to suction line 9 at a point between orifices l I and l2 so that regulator 5 will function by and in accordance with relative changes in draft losses across these orificesand damper 5 which in effect is also an orifice.

Variable orifice I2 is operated by a pressure responsive element, to be later described herein;

which is under the influence of pressure impulses received from an impulse line 3, which impulses are controlled by a master regulator M. R. and a relay P. R. and caused to vary by and in accordance with changes in load on the boiler. As the opening in the variable orifice is changed in response to changes in the load on the boiler, the suction. between orifices I l and I2 varies or changes. In response to such changes in suction, the suction responsive apparatus 8 of regulator 6 causes'the outlet damper 5 to be shifted to such a position that the suction in that portion of line 9 between orifices l l and i2 is restored to a value for which the regulator was originally adjusted to be in equilibrium; that is, regulator 6 shifts or adjusts the outlet damper to such a position that the suction in the line between orifices II in the liquid of the chamber I5.

The interior of float I6 is connected by pipe 20 to suction line 9 at a point between orifices H and I2 and the interior of float I1 is connected by a pipe 2! to the atmosphere. Therefore in response to the creation of suction in float E6 the float beam will rock clockwise.

In order that the float beam may come to rest in a position of stable equilibrium when the suction acting on float I6 is of a predetermined value,'the beam should be so loaded that such balance occurs at such value of suction. This leading may be accomplished by placing a balancing weight W on the float beam at some point tothe left of fulcrum l9. 7

With this arrangement, the float V beam will rock clockwise as the suction increases, with respect to the value of suction for which it was initially balanced, or counterclockwise, under the action of ,weight W as the suction decreases from said value.

Motor device 7 comprises a cylinder 25 in which a piston (not shown) is disposed and provided with a piston rod 26 to which a frame 2'! is attached. Frame 21 is connected by a rod 2B to the crank arm of the outlet damper 5. The piston in cylinder 25 may be operated hydraulically or bya fluid under pressure, such as compressed air, and the admission of such motive fluid to the cylinder at one side or the other of the piston is controlled by pilot valve 29 which is connected for operation to the float beam l8. This regulator as disclosed in the above-mentioned patent, includes a system of levers and linkages (not shown) which is operated in'response to the extent ,of movement of regulator frame 21, for returning the pilot valve to off position each time the regulator frame has been moved a distance proportional to the extent to which the valve is :opened in 'one or the other of its on positions.

That is, if the valve is opened a definite amount in one of its on positions, say in response to float it moving upwardly, the regulator frame moves upwardly a predetermined distance until the system of levers and linkagesabove mentioned, returns the valve to 01f position, at which time the regulator frame is brought to rest. If the valve is opened a deflniteamount in the other of its on positions in response to float 15 moving downwardly, the regulator-frame moves downwardly a predetermined distance, and shifts outlet damper 5 towards closed position, after which the valve is returned to off position by the system of, levers and linkages, above mentioned.

. Thus, regulator frame 21, under control of mechanism 8 will move either up or down in incremental, large or intermediate steps depending upon the extent of movement of float beam I8 to eifect step-by-step adjustment of damper 5 i the suction acting on float l6may be adjusted for a relatively small fraction of the value of suction at the furnace outlet. For example, if the suction at the furnace outlet is equal to ten inches of water, orifices I i and I2 may be so adjusted that the suction acting on float i6 is equal to only say one inch of water or any other fractional value of the suction at the furnaceoutlet which is sufficient to develop the power required to operate pilot valve 29. Thus when these orifices have been adjusted for a given value of draft and load demand, the suction acting on float IE will be maintained substantially constant at that value which places the float mechanism in balance.

.When a change in load occurs requiring a different value of draft, orifice I2 is adjusted, in

response to a change in the control impulses I transmitted to line [3, to a new position, thereby changing the suction between the orifices in line 9. The float mechanism immediately responds to this change in suction and causes regulator frame 21 to shift damper 5 to such a position a suction which is maintained at the furnace out-.

let.

Orifice H, as previously stated, is'fixed, but adjustable, that is, the area of the orifice is adjustable, but does notchange in area once it has been adjusted for-a particular area. This orifice may take various forms and as illustrated in Fig. 4, comprises an orifice body 38 which is tapped at its opposite ends for connection in line 9. The middle portion of the body has a relatively small bore 3! in which the orifice is located. Body 39 is tapped transversely of bore 3| for the reception of a threaded orifice plug 32, and this plug is preferably larger in diameter than bore 3! so that as the plug is screwed in or out, the orifice area is confined between the a lower end of the orifice plug and the wall of bore 3! immediately opposite the same. By turning orifice plug 32 in one direction or another, the size or area of the orifice may be adjusted and when once adjusted, the orifice plug is locked by means of a nut 33.

Orifice I2 is illustrated in Fig. 2 and comprises a valve body having a passageway 34 therein one end of which is open to the atmosphere and the other end of which is threaded as at 35 for connection to suction line 9. Within the valve body is an opening 36 in which a valve 3? is movably disposed for controlling the size of the opening or the area of the orifice in the passage above mentioned.

Valve 3?, as shown, is of cup-like form and provided with openings 38 in the wall thereof which cooperate with the wall of opening to define the area of the orifice. Valve 3? is secured to a tubular member 39 through which a stem d8 extends and on which the tubular member is threaded. Stem 48 extends upwardly through the valve body into a diaphragm chamber 4! which is closed at the top by means of a cap 32 bolted to the valve or orifice body. A flexible diaphragm 43 disposed in chamber 4! and having its outer edge clamped in pressure tight relationship between a member 44 and an annular shoulder 65 formed on the cap 52, forms the bottom of chamber ii. The central portion of the diaphragm is apertured to accommodate a bolt 56 the head 4'! of which rests on a thrust plate :38 secured to the upper end oi stem 40. The opening through which the bolt passes is sealed by means of washers 49 disposed on opposite sides of the diaphragm and between the head and nut of bolt die. A compression spring 5! disposed below thrust plate 48 works against the diaphragm so that as the pressure transmitted to the chamber t! varies, valve 3? will be shifted thereby varying the size of the orifice. The pressure impulses which operate on diaphragm 13 are transmitted on the diaphragm chamber by impulse line l3, which impulses are, as previously stated, varied by and in accordance with variations in the demand for steam or the load on the boiler.

In the system herein disclosed, when the boiler is operating at maximum load, the impulse pressure acting on diaphragm 43 is at its minimum value; and at minimum load, the impulse pressure acting on the diaphragm is at its maximum value. Therefore, in making the necessary adjustments of regulator G and the orifices H and i2, valve 3'] is adjusted by turning the tubular member 39 either up or down on stem 49 until the orifice in the passage through valve body is closed. Orifice H is opened wide after which the float mechanism of regulator 6 is loaded by adjusting weight W until damper 5 is adjusted to a position for minimum draft to be carried at the outlet of the boiler. The impulse pressure acting on diaphragm 42 is next adjusted to its maximum value which causes orifice 12 to open wide, after which orifice plug 32 of orifice ii is gradually closed until regulator 45 adjusts damper 5 to the position which will establish the minimum draft to be carried at the outlet of the furnace.

In the system herein illustrated, the rate at which air for combustion is supplied to the furnace is regulated by and in accordance with the draft at the outlet of the furnace. This is accomplished by means of a balanced float regulator 53 that responds to changes in the pressure in the combustion chamber of the furnace and adjusts a damper 54 disposed in a conduit 55 through which air passes from the supply pipe 3 to the furnace. Regulator 53 is similar in all respects to regulator 6 except that the loading weight W is omitted. For this reason, similar and corresponding parts are indicated by the same reference characters.

Regulator 53 is adjusted to maintain a predetermined pressure in the combustion chamber. If this pressure departs from that value, as occasioned by a change of position or setting of the outlet damper 5, regulator 53 responds and shifts damper 54 to such a position that more or less air is admitted to the furnace to reestablish the pressure in the furnace chamber at the desired value. Thus, if damper 5 is'being opened to increase the draft the pressure in the furnace chamber tends to fall, and to bring this pressure back to the constant value which is desired, the air control damper 5 3 is opened an amount sufficient to restore the pressure in the furnace to the desired value. Likewise, if outlet damper 5 is shifted towards closed position, the pressure in the furnace chamber tends to rise and in response to such rise in pressure regulator 53 shifts the air control damper 54 towards closed position, thereby reducing the amount of air delivered to the furnace and, consequently, the pressure in the furnace chamber is reduced.

Since the pressure in the furnace chamber is a measure of the air fiow through the furnace for a given value of draft at the outlet of the furnace, it follows that if regulator 53 maintains the furnace chamber pressure constant, the rate of air supply to the furnace will be directly proportional to the draft. Since the draft is regulated by and in accordance with the variations in steam pressure or the demand for steam, the rate of air supply will, therefore, be regulated by and in accordance with the demand for steam.

In order that regulator may respond to the pressure in the furnace chamber the interior of the inverted hell or float i5 is placed in communication with the combustion chamber of the furnace by means of a pipe or conduit 56 and the interior of the inverted bell or float i? is placed in communication with the atmosphere by means of a pipe 5?. Therefore, if the regulator 53 is adjusted to maintain the pressure in the furnace chamber at a value say equal to atmospheric pressure, the float beam of regulator 53 will be in balance when the pressures acting on floats i6 and E? are equal. Since the pressure acting on float ll does not change, any change in pressure acting on float it will cause the regulator to function and shift damper EL in the proper direction to estore the pressure to the balancing value.

The combustion regulating system illustrated also includes a regulator that regulates the rate of fuel delivery to the furnace by and in accordance with the demand for steam and this regulator is under the control of master regulator M. R. and a prcportioning relay P. R. Since the regulation of the sup, iy of fuel and the supply of air is by and in accordance with the demand for steam on the boiler, it follows that the supply of air i tel will bear the proper relation, one to the other, for ef icient combustion.

The master regulator M. R. is illus ed more or less in detail in Fig. 5; the props ioning relays P. R. and P.

S, which, as illustrated, are identical in construction, are illustrated more or less in detail in Fig. 6; and the fuel supply regulator 58 is illustrated in detail in g. 5. These devices will now be described in order.

The master regulator M. R. comprises a pressure-tight chamber 59 in which a bellows Si! is disposed. The bellows .is connected by a push rod ill to a knife edge 52 that bears against the under-side of a beam 53 which is fulcrumed on a knife edge t4 disposed to the left of knife edge 62 as seen in Fig. and bearing on the top of the beam. Steam pressure is conveyed to chamber lit by means of a pipe 65 and this pressure will compress, or collapse the bellows and cause beam 63 to turn about its fulcrum. The force exerted by the steam pressure, on and tending to turn beam is counter-balanced by means of a tension spring 66 one end of which is ancleared to a support El that is' adjustably connected to an adjustment screw 63 carried by a rigid The upper end of spring 66 is conmunicated to chamber 59, are utilized to operate a pilot valve l2 disposed in a three-way valve body 73. V

. Valve body '33 has an exhaust port '54, an inlet port '55, and an outlet port '56. The opposite ends of valve it are tapered and coast with the inlet and outlet ports to effect such a throttling action that for each position between wide open and closed positions, a definite pressure is maintained within the valve body and in the pipe line ll which is connected to the outlet port it. The opposits ends of the valve B2 are provided with extensions that extend through the outlet and inlet ports and serve as guides for the valve. The upper extension rests in a recess TS formed in the lower end of a stem is secured to a resilient strip til carried by beam 63. Valve 12 is urged upwardly by means of a coil spring 8! to ensure When valve if is in such a position as to com pletely close the inlet port 15 the pressures in pipe line Ti and in the interior of the valve body are equal to atmospheric; when the exhaust port is completely closed and the inlet port is wide open, the pressures in line ill and in the interior of the valve body are equal to the pressure of'the air in the supply pipe 82; and when valve l2 is in any position between those just mentioned the pressure in the pipe '52 will be of some intermediate value which is fixed by the rate at which air enters the valve body from the supply pipe 52 and exhausts from the valve body through the exhaust port.

The pressure impulses delivered by pipe ii to pro-portioning relay P. R. cause this relay to function and transmit pressure impulses to pipe line it and the value of these pressure impulses will bear a fixed relation to the pressure impulses transmitted to pipe line i? and these impulses in turn bear a fixed relation to the steam pressure acting on the diaphragm or bellows disposed in chamber H! of the master regulator M. R.

The proportioning relays P. R. and P. R. l are each of the same construction and function in substantially the same manner, and for this reason on y one relay has been shown in detail.

'As illustrated in Fig. 6 the proportioning relays,

each comprise a beam 85 which is fulcrumed on an ad stablefulcrum 86. Beam 35 is operatively connected to a pilot valve 8'? which transmits pressure impulses from a supply pipe 83 having having knife edge connections 92 and 93 with beam 85 on opposite. sides of fulcrum 85. Device 9i) comprises a chamber 94 in which a bellows 95 is disposed and which is subjected to the pres sure impulses delivered to pipe I? by the master regulator M. R. The bellows is connected by a push red as which is secured to a yoke 9?, to the lower end of which the knife edge 92 is secured. A compression spring 98 disposed between a rigid support '99 and the lower end of the yoke 9? acts in opposition to the forces exerted by bellows 95 on the yoke so that the net force exerted by knife edge 92 on beam 85 is equal to the dif= ference between the forces exerted by spring 98 and bellows 95 on yoke 91.

Device Q! is similar in construction to device 99 and for this reason similar elements are designated by similar reference characters primed. The interior of chamber 94' is connected to pipe line 89 so that the pressure transmitted to pipe line 89 also acts on bellows 95. The force exerted by knife edge as on beam 85 is equal to the difference between the forces exerted by spring 98 and bellows 95 on yoke Bl.

If the distances between fulcrum 86 and knife edges 92 and E are equal and springs 98 and 98' are adjusted to equal tensions, with'no pressure acting on bellows 95 and 95' beam 35 will be in balance and valve all will be'in position to shut off communication between the supply pipe and impulse line 89. If a pressure is transmitted to chamber t l, bellows 95 will contract and de: crease the force exerted by knife edge 92 on lever 85 causing the beam to turn counter-clockwise as seen in Fig. 6 and move valve 8? downwardly to place the supply pipe 88 in communication with pipe 89 and the interior of chamber 94'. The pressure in chamber as and pipe 89 will continue to increase until the force exerted by knife edge 93 is decreased to a value which is equalto the force exerted by knife edge 52 on beam 85 at which time the beam is placed in balance and the valve returned to off position. Ifthe pressure in chamber S4 is decreased the opposite action takes place in that knife edge 92 bears with greater force than knife edges 93 bear on beam 85, so that the lever is rocked clockwise as seen in Fig. 6, raising valve 8'! and placing pipe line' 89 and chamber $4 in communication with the atmosphere, thereby decreasing the pressure in both.

When this pressure has decreased to a value at which the forces of knife'edges 92 and 93 are in balance, the valve is again returned to closed position. Y

If, as stated previously herein, the distances between fulcrum 86 and knife edges 92 and 93 are equal and the areas of bellows 95 and 95' are equal, equal pressures in chambers 94 and at will place beam 85 in balance and hold valve in off-position, that is, in that position in which there no communication between pressure supply pipe 83 and pipe 6&3, or between pipe 89 and chambered and the atmosphere.

If fulcrum at is shifted longitudinally on its support screw S different pressures in chamber 9 than are transmitted to chamber 94, will place beam 85 in balance. In other Words, fulcrum 86 is shifted towards knife edge 93 higher pres sures will be required in chamber 94' than in chamber 94 to maintain beam 85 in balance. and

if the fulcrum is shifted towards knife edge 92 lower pressures in chamber 94' than in chamber 94 are required to place the beam in balance.

The pressure impulses transmitted to pipe 89 of relay P. R. are transmitted directly to diaphragm chamber 4| of the variable orifice I2 via pipe I3 and. to chamber 94 of relay P. R. I via pipe 'I'I which is connected to pipe I3. Pipe 89 of relay P. R. I is connected to the diaphragm chamber Ii!!! of regulator 58. The pressure impulses delivered to chamber I06 are utilized for operating a pilot valve IOI that controls the admission of motive fiuid to one side or the other of a piston working in a cylinder I92.

' Regulator 58operates in substantially the same manner as regulators 6 and 59 in that its frame I03 which is carried by piston rod I04 effects step by step adjustment in either direction of the fuel supply or feeding mechanism 2.

Since the proportioning relays may be adjusted to send control impulses to apparatus to be controlled thereby, which bear a fixed adjustable relation to the impulses received by the diaphragm chamber 94- thereof, it follows that the pressure impulses delivered to the diaphragm chamber of orifice I2 and to the diaphragm chamber I of the fuel regulator 58 will bear a fixed relation to each other and that the proper relation between the supply of fuel and the supply of air will be maintained throughout the full operating range of the boiler. The pressure impulses transmitted to pipe lines I 3 and 89 will also bear a definite or fixed but adjustable relation to variations in the steam pressure of the boiler, because the pressure impulses transmitted to pipe line 'I'I connected to valve body I3 associated with the master regulator M. R. bear a direct relationship to the steam pressure acting on the bellows disposed in diaphragm chamber 59.

Pilot valve IGI of regulator 58 is connected in operative relationship to a diaphragm I 05, which forms the bottom of diaphragm chamber IUD, by means of a stem I98. The diaphragm operates against a compression spring I91, one end of which is disposed in a socket I08 which is raised or lowered, depending on the direction of travel of the regulator frame I93, by means of a bell crank I09 secured to cylinder I02 and operated by an angling bar IIB carried by frame I 93. If the pressure impulses delivered to chamber I68 are increasing, the diaphragm will move downwardly and operate pilot valve I [H in such direction that regulator frame I03 moves upwardly. As the frame moves upwardly bell crank I (I9 is turned clockwise thereby raising socket I08 and compressing spring IIl'I an amount sufiicient to return the pilot valve to its off position, at which time the regulator frame comes to rest. If the pressure impulses delivered to chamber I39 continued to increase the same action is repeated so that step-by-step movement of the regulator frame in an upward direction is effected.

If the pressures delivered to chamber Ififi are decreasing the pilot valve is moved upwardly under the action of spring I97, with the result that frame I93 moves downwardly. As the frame moves downwardly, socket I 98 is moved downwardly by bell crank I09 so that the force exerted by spring I9! against the diaphragm is decreased by an amount suificient to allow the diaphragm to return the valve to off position. If the pressures continue to decrease, the action just described is repeated so that step-by-step movement of the regulator in a downward direction is effected.

In Fig. 1, a proportioning relay P. R. 2, is shown, chamber 94 of which is connected to a pipe line i I2 which in effect is an extension of pipe line I3. This proportiom'ng relay would be utilized to transmit impulses to a pipe line H3 for controlling the operation of a fuel supply regulator, such as indicated at 58, associated with another boiler, while pipe line I I3 would lead to a variable orifice such as indicated at I2, associated with the draft regulator of another boiler. In other words, by means of a single master regulator M. R. one proportioning relay P. R. and a plurality of proportioning relays P. R. I, P. R. 2, etc. a whole group of boilers could be controlled, the number of boilers controlled being equal to the number of proportioning relays P. R. I, P. R. 2, etc. employed. Since the proportioning relays are individually adjustable and since the variable orifices I2 are also individually adjustable, each boiler in the group or bank could be operated at the same or different ratings, and each would supply its proportionate share of steam to the main steam header for the group.

Orifices II and I2 may also be utilized to vary the air pressure in duct 3 by and in accordance with the load, in which case regulator 53 and its damper 5 5 may be rendered more efficient in the regulation of the furnace air supply. In Fig. '7, a control system is shown in which orifices II and I2 are employed for this purpose. These orifices are connected in a conduit or pipe line I53 between which the float responsive mechanism B of a regulator I I9 is connected. Regulator I i9 operates a damper I29 disposed in air supply conduit 3 to which a forced draft fan or blower I2I, driven by a motor I22, is connected. Regulator H9 operates to so adjust damper I20 that the pressure between orifices II and I2 is maintained substantially constant at some predetermined value, say for example, one inch of water. In so adjusting damper I20, the pressure of the air in that portion of duct 3 between dampers 54 and I 29, is caused to vary by and in accordance with the load on the boiler (because orifice I2 would be under the control of a master regulator M. R... as in Fig. 1). While regulator II9 will maintain the pressure between orifices II and I2 at a constant value of say one inch of water, the pressure in the duct 3 would, at high boiler ratings, be higher than one inch of water and, at low ratings, would be equal to or approximately equal to one inch of water. Since the pressure in this portion of duct 3 is varied in this manner, it is possible to confine the operation of damper 54 within its most efficient regulating range (usually the middle of its range) for all values of load or rating at which the boiler is required to operate.

In this arrangement, air flows from duct 3 to line I8 and orifices II and I2 to the atmosphere; therefore, the pressure in line II8 between these orifices to which the float mechanism of regulator I19 responds, is dependent on the relative pressure drop across these orifices which in turn, is dependent on the pressure in duct 3 as effected by the position of damper I 20 and the size of the opening or passage through orifice I2.

But, since regulator I I9 operates to maintain the pressure between orifices II and I2 constant, it follows that any change in pressure in duct 3 as effected by a change in position of damper 54, will result in a change in pressure between these orifices, and such change in pressure will cause regulator II9 to shift damper I25 to. that position which will restore the pressure, between these orifices to the constant value for which the regulator is adjusted to maintain. 7

Likewise, any change in size of the passage through orifice I2, as effected by a change in load or demand for steam. on the boiler, will result ina change in pressure between orificesll and I2.

As a consequence, regulator I I9 will shift damper I20 to such a position that the pressure in duct 3 is adjusted to a value that will establish and. restore the pressure between orifices H and I2 to that constant value for which it is adjusted to maintain. a

If, for a given setting or adjustment of orifice I2 and damper I25, a change in pressure in duct 3 is occasioned by a change in position of damper 54, in response to a change in draft at the outlet of the furnace, either as the result of a change in load on the boiler, .or for any other reason, a change in pressure will occur in line H8 between these orifices and effect such adjustment of damper I29, through the agency of regulator H9,

, lator H9 and adjustment of damper I20 as will restore the pressure between orifices II and I2 to'a preselected constant value and thereby maintain the pressure in duct 3 at the proper value. Not only is the pressure in duct 3 maintained at the proper value for all furnace operating requirements, but it also makes possible the operation of damper 54 in that range of its travel where y it is most efficient from the standpoint of regulating the rate at which air is supplied to the furnace. In Fig. 8, the invention has been shown in an embodiment which provides for the control of a plurality of different fuel supplies for the furnace, and the draft, by and in accordance: with the load, and consequently, for the regulation of the air supply by and in accordance with the total amount of the fuels supplied to the furnace. In this figure, apparatus 2 feeds solid fuel to the furnace and is under the control of regulator 58, master regulator M. R. and proportioning r'elays P. R. I and. P. R. 2, as in Fig. 1. Another supply of fuel, such as gas, is provided for the furnace. The gas is delivered from a main header I 25, (which maysupply a bank of furnaces) through a pipe I26 in which a control damper I2? is disposed; Damper I2! is operated by a regulator I28 under the control of a master regulator M. R. 2, like master regulator M. R., so that the supply of gas to the furnace is regulated by and in accordance with the demand for steam, regulator M. R. 2 being connected to steam header H. i

The air required for combustion is supplied by a duct 3 through a duct 55 to the furnace, a damper 54 controlled by regulator 53 adjusting the rate of air.supply so as to maintain the pressure in the furnace combustion chamber substantially constant. The control for the air supply, as shown, is the same as that shown and described in connection with Fig. 1.

' As disclosed in connection with the apparatus of Fig. 1, the draft at the ,outlet of the furnace is controlled by and in accordance with the demand for steam and that the rate of air supply being dependent on the draft, is also controlled by and in accordance with the demand for steam. Where two or more different fuels are supplied to the furnace, the rate of air sup employed.

To accomplish this type of control, an adjustable orifice is provided for each fuel supply (these orifices being designated as I2a and lZb,

but which are of the same type as orifice I2 of Fig. 1), each orifice being under the control of r a master regulator and a proportioning relay.

Orlfices I 211 and I2b are connected in parallel to each other by branch pipes I30' and HM, but.

in series with a suction line 9 having a fixed orifice II therein between orifices l2a and I2b and the end of the pipe line which isconnected to the furnace outlet;

Orifice I 2a is operated by pressure impulses transmitted to line I3 by relay P. R. as effected by master regulator M. R., While orifice I211 is operated by pressure impulses transmitted to line I32 by a proportioning relay P. R. b. as effected by pressure impulses transmitted to line I33 by master regulator M. R. 2. Thus orifices f I20. and 521) are adjustedby and in accordance with the amount of fuel delivered to the" furnace by apparatus 2 and the supply source of gaseous fuel, respectively. Since orifices IZ-a' and 'I2b are in parallel, it will. be apparent that the resistance offered to the fiow of' atmospheric air to orifice I I will be proportional to the product of the resistances of orifices IZa and 12b divided bythe sum of their resistances.

Since the amount of air passing through line 9' is dependent on the flow resistance offered by draft at the outlet of the furnace as effected by the setting of the outlet damper 5 will vary by and in accordance with the load and the total amount of the several fuels delivered to the furnace. Since the amount of air delivered to the furnace is dependent on the draft, it also follows that the proper relation between the rate of air supply and the rate of total fuel supplied to the furnace will be maintained. j

As in the case of regulator 'I and fioat mechanism 8 of Fig. 1, which operates to maintain a constant pressure between orifices II and I2, regulator I and float mechanism 8 in Fig. 8 will so adjust outlet damper 5 that the constant pressure is maintained between orifices II and I2a-I2b'. r 1

In the system shown in Fig. 8, master regulator M. R. 2 may be given a different calibration than regulator M. R. so that no gaseous fuel is supplied to the furnaceuntil the fuel supply mechanism 2 has reached its maximum capacity, or master regulator M. R. 2 and its associated relay P. R. b. may be adjusted or calibrated to effect the delivery of gaseous fuel throughout either the entire range, or any part of the operating range of fuel feeding apparatus 2.

rom the description of the various embodi- 'ments of the invention, it will be apparent that the same type of regulator may be employed in all cases where orifices Ii and i201 II and I 211., I212 are utilized because the pressures whether positive or negative, to which the fioatmechanisms respond are substantially constant and may be entirely different in value from the pres- 75 sure conditions undergoing regulation. The only time that these float mechanism actuating pressures (positive or negative) would be comparable to the controlled pressures (positive or negative) would bewhen the controlled pressures are equal to or nearly equal to the pressures between the control orifices H and it, or H and 2(t2b. But even in that case the fioat mechanism actuating pressures would be within the operating range as these pressures are held to a substantially constant value.

In Figs. 7 and 8 substantially the same type of regulators and control orifices are illustrated as were described in connection with Fig. 1. Therefore, such regulators and other apparatus illustrated in Figs. 7 and 8 which are the same as in Fig. 1 will have the same reference characters applied thereto to indicate the same parts and elements that are shown and described in connection with Fig. 1. Since the mechanisms illustrated in Figs. 7 and S are for the most part similar to those described in connection with Fig. 1, further detailed description of structure and operation is believed unnecessary.

Whil several forms of the invention have been shown and described herein it will be appreciated by those skilled in this art that various modifications and changes may be made without departing either from the spirit or the scope of the invention. It is desired, therefore, that only such limitations shall be placed on the invention as are imposed by the prior art and the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In combination, a regulator having a suction responsive element adjusted for equilibrium at a predetermined value of suction for causing the regulator to move in one direction or another in response to a departure of the suction from said value, a suction line having one end connected to furnace outlet and the other open to the atmosphere, fixed and adjustable orifices in the suction line and a damper in the furnace outlet operated by the regulator, a connection between said orifices to the suction element of the regulator, and means responsive to a condition to be controlled for adjusting the adjustable orifice, said regulator being operated in response to such adjustment to shift the damper and restore the suction in the line between said orifices to said predetermined value.

2. In combination, a source of suction, a conduit connected to said source, means for adjusting the suction at the point of connection to the source, spaced orifices in said conduit, means for adjusting one of said orifices to vary the suction in the conduit between said orifices in accordance with a condition to be controlled, and means responsive to a change in suction in the conduit between said orifices for adjusting the suction source to restore the suction in the con duit between the orifices to the value which existed therein before the change in adjustment of the adjustable orifice was made.

3. In apparatus for regulating the suction at the outiet of boiler furnace, the combination with an outlet damper and a regulator for adjusting the damper, of a suction line connected at one end to the outlet of the furnace and having the other end open to the atmosphere, a fixed orifice in said line, an adjustable orifice between the fixed orifice and the open end of said line, suction responsive mechanism connected to the line between said orifices and adjusted to shift the damper to such position as will maintain the suction in the portion of the line between said orifices substantially constant, means responsive to variations in load on the boiler for adjusting the adjustable orifice by and in accordance with such load changes.

4. The combination with a boiler furnace having fuel supply regulating apparatus, draft regulating apparatus, a source of air supply, and means for regulating the air supply by and in accordance with the draft at the furnace outlet, of means for controlling the fuel supply and draft regulating apparatus by and in accordance with the demand for steam, the controlling means for the draft regulating apparatus comprising a suction line connected at one end to the furnace utlet and having its opposite end open to the atmosphere, a fixed orifice in said line and an adjustable orifice between the open end of the suction line, and the fixed orifice, and a connection from the draft regulating apparatus to the suction line at a point between the orifices, said draft regu ating apparatus being adjusted to maintain the suction between the orifices constant, and means responsive to and under the control of the steam responsive controlling means for adiusting the adjustable orifice by and in accordance with the demand for steam.

5. In combination, a duct, means for passing gaseous medium through the duct, a regulating element in the duct for regulating said medium, a conduit connected at one end to said duct and open to the atmosphere at the other through which a gaseous flow takes place, a variable orifice and a fixed orifice in said conduit, the fixed orifice being between the duct and the variable orifice, mechanism responsive to the pressure between said orifices for operating the duct regulating element to maintain a substantially constant pressure between the orifices, and means for operating said variable orifice in response to changes in a condition affected by the ledium passing through said duct.

6. In regulating apparatus, the combination with a main duct, means for passing a gaseous medium through the duct, and a regulating element in the duct for regulating said medium, of an auxiliary conduit connected in parallel to the duct in fiow communication therewith, a variable orifice and a fixed orifice in the conduit on the discharge side of the variable orifice, means for adjusting the variable orifice in accordance with a variable condition to thereby vary the pressure between said 01 and means responsive to a change in pressure between the orifices for adjusting the regulating element in said duct by and in accordance with such change in pressure so as to maintain the pressure between said orifices substantially constant.

7. In combination with a furnace, a duct in which a gaseous medium essential to combustion is carried under positive rcssure, a source of supply of such medium, dampers at sace points in said duct and located bet---m source of supply and the inlet furnace, auxiliary conduit ccnn. to duct at a point between said dampers, said conduit havin an adjustable orifice and a fixed orifice between the adjustable orifice and the duct, and means responsive to changes in pressure between said orifices for so adjusting one of said dampers that the pressure between orifices is maintained substantially constant.

8. In combination with a furnace, a duct in c.)

which a gaseous medium essential'to combustion is carried under positive pressure, a source 7 of supply of such medium, dampers at spaced points in said duct and located between the source of supply and the inlet thereof to the furnace, an auxiliary conduit connected to the duct at a point between said dampers, said conduit having an adjustable crifice and a fixed orifice between the adjustable orifice and the duct, means responsive to changes in pressure between said orifices for adjusting one of said dampers that the pressure between said orifices is maintained substantially constant, and means responsive to a condition requiring a change in the rateiof furnace combustion for adjusting said adjustable orifice to effect a change in pr ssure between said orifices.

9a In combination with a furnace, a duct in which a gaseous medium essential to combustion is carried under positive pressure, a source of supply of such medium, dampers at spaced points in said duct and located between the source of supply and the inlet thereof to the furnace, an

auxiliary conduit connected to the duct at a point between said dampers, said conduit having an'adjustable orifice and a fixed orifice between the adjustable orifice and the duct, means for so adjusting one of said dampers that a predetermined pressure condition is maintained in the furnace combustion chamber, and means respon- V sive to a change in pressure between saidorifices a point between said dampers; said conduit having an adjustable orifice and a" fixed orifice between the adjustable orifice and the duct, means for so adjusting one of said dampers that a predetermined pressure condition is maintained in the furnace combustion chamber, means responsive to a change in pressure between'said orifices as affected by the adinstment of said dampers for so adjusting the other of said dampers thatisuch a change in pressure will be afiected in said duct as will maintain the pressure between said 'orifices substantially constant, and means respon-, sive to a condition requiring a change in the rate of'furnace combustion for adjusting said adjustable orifice to effect a change in pressure between said orifices. I

11. A control system for furnaces having a plurality of sources of supply of different fuels, a regulatable source of air'supply,; a draft regulating element in the outlet of the furnace, means responsive to variations pressure in the combustion space of the furnace for regulating the air supply to maintain a substantially constant pressure in said space, and means responsive to the demand for combustion for regulating the sources of fuel supply in accordance with such demand, of means'under the control of the combustion demand responsive means for controlling the draft regulating element by and in accordance with the total rate at which fuel is delivered o by said sources of supply to the furnace.

12. A control system for boiler furnaces havaocasre ing a plurality of sources of supply of different fuels, a regulatable source lof air supply, 'a draft regulating element in the putlet of the furnace,

'means responsive to variations in pressure in the combustion space of the furnace for regulating the air supply to maintair i a substantiallycconstant pressure in; said space, a regulator responsive to the demand for steam for regulating one of said sources of fuel supply, a regulator responsive to theldemand for steam for regulating another of sa'id sources of supply in acl cordance with the, demand for steam, of means under the joint control of the steam demand responsive regulators for controlling the draft regulating element by and in accordance with the total rate at which fuel is delivered to the furnace by said sources of supply. i l

113. A cdntrol system for boiler furnaces having alplurality of sources of supply of diiferent fuels,

later responsive to'the dei hand forfsteam for reg- 'ulating another of said sources of supply in accordance with the demand for steam, of an air flow conduit connected tothe outlet of' the furnace and having a pressure differential there across substantially equal to the draft loss occurring in the furnace from the combustion space to the furnace outlet, a plurality of adjustable orifices'in said conduit, an adjustable orifice between said adjustable orifices and the furnace outlet, one of said orifices being actuated by one of the steam demand responsive regulators and another being actuated by another of said steam demand responsive regulators, and means responsive to the pressure in said conduit adjacent the upstream side of the fixed orifice for so adjusting theidraft regulating element that a substantially constant pressure is maintained between said adjustable and fixed orifices. g

I 14. Acontrol system for boiler furnacesfhaving a plurality of sources of supply of different fuels, a regulatable source of air supply, a draft reguiating element in the outlet of theifurnacej means responsive to variations in pressure in the combustion space of the furnace for regulating the air supply to maintain a substantially constant pressure in said space, a regulator responsive to the demand for steam for regulating one of said sources of fuel supply in accorda ice withthe demand for steam, a regulator responsive to the demand for steam for regulating another of said sources of fuel supply'ingaccordance' withthe demand for steam,'of was flow conduit having 7 one end connected to the furnace outlet and the other end connected to a plurality of parallel branch pipes which are open to the atmosphere, adjustable orifices in the branch pipes and a fixed V orificein the conduit, means operated by one ofthe steam demand responsive regulators for 'ment that a substantiallyponstant pressure is maintained in the conduit between said fixed and adjustable orifices.

15. In a control system, a plurality of conduits connected in parallel to carry a fiowing medium, a regulating element in one of said conduits between the points of parallel connection so that a change in flow through the conduit having said regulating element therein causes a change in flow through another of said conduits, a fixed orifice in said latter conduit and an adjustable orifice therein on the upstream side of the fixed orifice, means for regulating the adjustable orifice in accordance with a condition to be controlled thereby to change the pressure between said orifices, and means responsive to the change in pressure between said orifices for adjusting said first mentioned regulating element so as to maintain the pressure drop across the adjustable orifice substantially constant.

16. In combination, a plurality of conduits carrying a flowing medium and a single conduit into which said plurality of conduits deliver said medium, a regulating element in one of said conduits, an adjustable orifice and a fixed orifice in another of said conduits, the fixed orifice being on the discharge side of the adjustable orifice, means for regulating the adjustable orifice in accordance with a condition to be controlled, and means responsive to the pressure between said orifices for adjusting said regulating element so as to maintain the pressure drop across the adjustable orifice substantially constant.

GEORGE W. SMITH. 

